Transcript ExploringMagnetism-BEK (1) File

EXPLORING MAGNETISM
What is a Magnet?
What Materials are Magnetic?
What Materials are Magnetic?
What Do Magnets Do?
Attract or repel other magnets (exert a
force)
Attract other magnetic metals
Have 2 distinct ends (poles) – N and S
Like poles repel, opposite poles attract
Notes:
Magnets do not need to touch to exert force (can exert
force through empty space)
They can turn other magnetic metal objects into temporary
magnets
Magnetism in a Magnet
When elements like Fe form solids, they form crystalline
structures with little domains of many, many atoms all
aligned in the same direction. Each domain is like a mini
magnet. When all the domains are allowed to align, the
whole object takes on a large-scale magnetic field.
Magnetic Field Lines
Magnetic field of a bar
magnet: 2 poles, called
North and South
Dipole field
Field has direction: lines
point away from N and
toward S
Definition of a Pole: Where lines meet
(converge)
e.g.: lines of longitude on a globe meet
at poles
Earth: A Huge Bar Magnet
Magnet
Moving molten
iron in Earth’s
outer core
causes most of
Earth’s magnetic
field.
Magnetic field
poles are NOT
aligned with
geographic
poles. They also
wander and flip
(500,000 yrs between
flips, 10,000 yrs to
complete flip).
Activities: Investigating magnetism
Collect for your group: 2 bar magnets, a nail, some paperclips,
iron filings, an OHP transparency sheet.
What to do:
1. Try using a magnet to pick up some paper clips and also try
holding it near some iron filings.
2. Find out what happens when you put 2 N poles, 2 S poles
and a N and S pole of the two magnets together.
3. Place a magnet under the OHP sheet and scatter iron filings
over it. Draw what you observe on p86 of your Sci Pad.
4. Repeat Activity 3 using both magnets arranged as in Activity
2 (but without the magnets actually touching). Draw on p87.
5. Try to magnetise the nail by stroking it several times in one
direction with one of the magnets. Can you pick up paper
clips with the nail? Drop the nail on the floor then try it again.
ELECTRICITY  MAGNETISM
Electric currents cause magnetism
•
How can you tell?
Compass needle moves when
near electrical current creating an magnetic field
ELECTROMAGNET
A magnet with a field produced by an electric current
Electromagnetism
a moving charge (electricity)
produces a magnetic field
•
More coils of wire=
more current =
stronger magnet
•
Bigger battery =
stronger magnet
Making an electromagnet
Collect for your group: a battery, some copper wire, a nail
and some paperclips.
What to do:
1. Wind the copper wire tightly around the length of the
nail leaving about 10 cm of wire free on each end.
2. Hold the wire wrapped nail near the paperclips and see
if it will pick them up.
3. Attach the free ends of the wire to the battery terminals.
4. Repeat step 2 with the wire wrapped nail attached to
the battery and note what happens.
5. How could an electromagnet be useful?
MAGNETISM  ELECTRICITY
A moving magnet can generate electricity
•
How can you tell?
Electromagnetic induction
moving a magnet in and out of a
coiled wire creates an electrical
current without using a battery.
This principle is used to
generate electricity. Water,
wind or steam are used to
move huge magnets which
produces an electric current.
Generating Electricity
• https://www.youtube.com/watch?v=20Vb6
hlLQSg (Energy production)
• https://www.youtube.com/watch?v=d_aTC
0iKO68 (Electric motors and generators)
• https://www.youtube.com/watch?v=AmWE
s5CTQ3Q (How is electricity produced?)
• https://www.youtube.com/watch?v=E8QF8
uRCEtE (How is electricity produced?)
• https://www.youtube.com/watch?v=NsQiVI
Py6CA (Electricity production – for kids)